Neutron matter properties from relativistic Brueckner-Hartree-Fock theory in the full Dirac space

A novel description of the strongly interacting pure neutron matter(PNM)was carried out by the relativistic Brueckner-HartreeFock(RBHF)theory in the full Dirac space with Bonn A potential.The scalar and vector components of the single-particle potentials are shown as functions of the momentum and the density,and are compared with the results obtained by the RBHF calculations in the Dirac space without negative-energy states.By benchmarking the binding energies of PNM to those predicted by several ab initio methods in the nonrelativistic framework with two-and three-body forces,we find our results are softer than those from the Brueckner-Hartree-Fock theory with the inclusion of three-body force,and in harmony with the ones obtained by the Monte Carlo method and many-body perturbation theory within uncertainties.In addition,the equation of state for neutron star matter is consistent with the constraints from multi-messenger astrophysical observation and heavy-ion collision experiments.The tidal deformabilities of a binary neutron star system are calculated and found consistent with the constraints from GW170817.

Finite particle number description of neutron matter using the unitary correlation operator and high-momentum pair methods

Using bare Argonne V4'(AV4'),V6'(AV6'),and V8'(AV8')nucleon–nucleon(NN)interactions,the nuclear equations of state(EOSs)for neutron matter are calculated with the unitary correlation operator and high-momentum pair methods.Neutron matter is described using a finite particle number approach with magic number N=66 under a periodic boundary condition.The central short-range correlation originating from the short-range repulsion in the NN interaction is treated by the unitary correlation operator method(UCOM),and the tensor correlation and spin-orbit effects are described by the two-particle two-hole(2p2h)excitations of nucleon pairs,where the two nucleons with a large relative momentum are regarded as a high-momentum(HM)pair.With increasing 2p2h configurations,the total energy per particle of the neutron matter is well-converged under this UCOM+HM framework.Comparing the results calculated with AV4',AV6',and AV8'NN interactions,we demonstrate the effects of the short-range correlation,tensor correlation,and spin-orbit coupling on the density dependence of the total energy per particle of neutron matter.Moreover,the contribution of each Hamiltonian component to the total energy per particle is discussed.The EOSs of neutron matter calculated within the present UCOM+HM framework agree with the calculations of six microscopic many-body theories,especially the auxiliary field-diffusion Monte Carlo calculations.

Effects of Tensor Couplings on Nucleonic Direct URCA Processes in Neutron Star Matter

The relativistic neutrino emissivity of the nucleonic direct URCA processes in neutron star matter is investigated within the relativistic Hartree-Fock approximation. We particularly study the influences of the tensor couplings of vector mesons ω and ρ on the nucleonic direct URCA processes. It is found that the inclusion of the tensor couplings of vector mesons w and p can slightly increase the maximum mass of neutron stars. In addition, the results indicate that the tensor couplings of vector mesons ω and ρ lead to obvious enhancement of the total neutrino emissivity for the nucleonic direct URCA processes, which must accelerate the cooling rate of the non- superfluid neutron star matter. However, when considering only the tensor coupling of vector meson ρ, the neutrino emissivity for the nucleonic direct URCA processes slightly declines at low densities and significantly increases at high densities. That is, the tensor coupling of vector meson ρ leads to the slow cooling rate of a low-mass neutron star and rapid cooling rate of a massive neutron star.

Deconfinement Phase Transition Including Perturbative QCD Corrections in (Proto)neutron Star Matter

Deconlinement phase transition and neutrino trapping in （proto）neutron star matter are investigated in a chiral hadronic model （also referred to as the FST model） for the hadronic phase （HP） and in the color-flavor-locked （CFL） quark model for the deconlined quark phase. We include a perturbative QCD correction parameter αs in the CFL quark matter equation of states. It is shown that the CFL quark core with K^0 condensation forms in neutron star matter with the large value of αs. If the small value of αs is taken, hyperons suppress the CFL quark phase and the liP is dominant in the high-density region of （proto）neutron star matter. Neutrino trapping makes the fraction of the CFL quark matter decrease compared with those without neutrino trapping. Moreover, increasing the QCD correction parameter as or decreasing the bag constant B and the strange quark mass ms can make the fraction of the CFL quark matter increase, simultaneously, the fraction of neutrino in protoneutron star matter increases, too. The maximum masses and the corresponding radii of （proto）neutron stars are not sensitive to the QCD correction parameter αs.

Isospin dependence of nucleon effective masses in neutron-rich matter

In this talk,we first briefly review the isospin dependence of the total nucleon effective mass M Jinferred from analyzing nucleon-nucleus scattering data within an isospin-dependent non-relativistic optical potential model,and the isospin dependence of the nucleon E-mass M;E J obtained from applying the Migdal–Luttinger theorem to a phenomenological single-nucleon momentum distribution in nuclei constrained by recent electron-nucleus scatteringexperiments.Combining information about the isospin dependence of both the nucleon total effective mass and E-mass,we then infer the isospin dependence of nucleon k-mass using the well-known relation M_J~*=M_ J^(*1E).Implications of the results on the nucleon mean free path in neutron-rich matter are discussed.

The Brueckner-Hartree-Fock Equation of State for Nuclear Matter and Neutron Skin

The equation of state for nuclear matter is presented within the Brueckner Hartree-Fock （BHF） scheme, by using the realistic Argonne VI8 or Bonn B two-nucleon potentials plus their corresponding microscopic three-nucleon forces. It is then applied to calculate the properties of finite nuclei within a simple liquid-drop model, and we compare the calculated volume, surface, and Coulomb parameters with the empirical ones from the liquid drop model. Nuclear density distributions and charge radii in good agreement with the experimental data are obtained~ and we predict the neutron skin thickness of various nuclei.

EOS of neutron-rich matter and pure neutron matter

We report the equation of state(EOS) of pure neutron matter(PNM) and neutron-rich matter(NRM) for the realistic Urbana V 14 two nucleon interaction,obtained by using a Variational Monte Carlo(VMC) method.Also,many body interactions are included as a phenomenological density dependent term in the potential.The binding energy per nucleon is calculated for different densities and various isospin asymmetry parameters.Our results on NRM and PNM are compared with relativistic Brueckner-Hartree-Fock theory and relativistic Hartree-Fock model with the unitary correlation operator method.The results obtained in this study show reasonable agreement with both of these relativistic Hartree-Fock approaches.We also compare the binding energies obtained in this study with those obtained by various authors employing different methods and techniques.

Constraints on Estimation of Radius of Double Pulsar PSR J0737-3039A and Its Neutron Star Nuclear Matter Composition

The aspect of formation and evolution of the recycled pulsar（PSR J0737-3039 A/B） is investigated, taking into account the contributions of accretion rate, radius and spin-evolution diagram（- diagram） in the double pulsar system. Accepting the spin-down age as a rough estimate（or often an upper limit） of the true age of the neutron star, we also impose the restrictions on the radius of this system. We calculate the radius of the recycled pulsar PSR J0737-3039 A ranges approximately from 8.14 to 25.74 km, and the composition of its neutron star nuclear matters is discussed in the mass-radius diagram.

Magnetic Charge Theory. Part 3: Neutron Structure and Dark Matter Source

The concept of magnetic charge is further developed to explain the electron/proton magnetic bonding that forms the neutron. The derivation leads to a minimum range for the Coulomb force of 2.35 fm that explains the lack of the Coulomb force in the nucleus. Further investigation into the nature of gravity leads to the possibility that dark matter is a byproduct of stars.

Observational Constraints on Quark Matter in Neutron Stars

We study the observational constraints of mass and redshift on the properties of the equation of state （EOS） for quark matter in compact stars based on the quasi-particle description. We discuss two scenarios; strange stars and hybrid stars. We construct the equations of state utilizing an extended MIT bag model taking the medium effect into account for quark matter and the relativistic mean field theory for hadron matter. We show that quark matter may exist in strange stars and in the interior of neutron stars. The bag constant is a key parameter that affects strongly the mass of strange stars. The medium effect can lead to the stiffer hybrid-star EOS approaching the pure hadronic EOS, due to the reduction of quark matter, and hence the existence of heavy hybrid stars. We find that a middle range coupling constant may be the best choice for the hybrid stars being compatible with the observational constraints.

The Neutron and Dark Matter in the Standard Model of Particle Physics

The existence of the neutron, originally postulated to justify the stability of the nucleus, is very similar to the postulation of Dark Matter to give stability to galaxies and galaxy clusters. However, the existence of the neutron has been proven as an important part of the nucleus that is linked within its integral structure in the Standard Model of Particle Physics. The Standard Model that began with the electron and the proton, currently, with more than one hundred particles, shows in some parts, cracks that induce to reconsider the veracity of the theories and models. Here it is established that all theories are to some extent false and therefore, so will any model, which is always a specific part of the theory. Also, like several other things, by means of a mathematical calculation, it is clarified why, it has not been possible to incorporate the Dark Matter within the Standard Model. Furthermore, it is reliably demonstrated that the introduction of the Dark matter postulate is superfluous and that the high speeds of stellar rotation determined experimentally are analytically explained with the stellar dynamics described here.

The Equation of State of Nuclear Matter and Neutron Stars Properties

The equation of state (EOS) of symmetric nuclear and pure neutron matter has been investigated extensively by adopting the non-relativistic Brueckner-Hartree-Fock (BHF). For more comparison, the extended BHF approaches using the self-consistent Green’s function approach or by including a three-body force will be done. The EOS will be studied for different approaches at zero temperature. We can calculate the total mass and radius of neutron stars using various equations of state. A comparison with relativistic BHF calculations will be done. Relativistic effects are known to be important at high densities, giving an increased repulsion. This leads to a stiffer EOS compared to the EOS derived with a non-relativistic approach.

Why the Central Monster in M87 Should Be a Massive DEO Rather than a SMBH?

In this paper, we show that massive envelopes made of highly compressed normal matter surrounding dark objects (DEOs) can curve the surrounding spacetime and make the systems observationally indistinguishable from their massive black hole counterparts. DEOs are new astrophysical objects that are made up of entropy-free incompressible supranuclear dense superfluid (SuSu-matter), embedded in flat spacetimes and invisible to outside observers, practically trapped in false vacua. Based on highly accurate numerical modelling of the internal structures of pulsars and massive neutron stars, and in combination with using a large variety of EOSs, we show that the mass range of DEOs is practically unbounded from above: it spans those of massive neutron stars, stellar and even supermassive black holes: thanks to the universal maximum density of normal matter, , beyond which normal matter converts into SuSu-matter. We apply the scenario to the Crab and Vela pulsars, the massive magnetar PSR J0740 6620, the presumably massive NS formed in GW170817, and the SMBHs in Sgr A* and M87*. Our numerical results also reveal that DEO-Envelope systems not only mimic massive BHs nicely but also indicate that massive DEOs can hide vast amounts of matter capable of turning our universe into a SuSu-matter-dominated one, essentially trapped in false vacua.

Effect of an electron gas on a neutron-rich nuclear pasta

We studied the role that electron gas has on the formation of nuclear structures at subsaturation densities and low temperatures(T<1 Me V).Using a classical molecular dynamics model we studied isospin symmetric and asymmetric matter at subsaturation densities and low temperatures varying the Coulomb interaction strength.The effect of such variation was quantified on the fragment size multiplicity,the inter-particle distance,the isospin content of the clusters,the nucleon mobility and cluster persistence,and on the nuclear structure shapes.We found that the presence of an electron gas distributes matter more evenly,disrupts the formation of larger objects,reduces the isospin content,and modifies the nucleon average displacement,but does not affect the inter-nucleon distance in clusters.The nuclear structures are also found to change shapes by different degrees depending on their isospin content,temperature and density.

Influence of Interactions on Populations for Hyperons in Neutron Stars

The numerical results of the populations for the baryon octet in neutron star matter have been presented by solving a set transcendental equations in the framework of the relativistic mean field approximation. The influence of the hyperon interactions on hyperon populations in neutron star matter is discussed. The results manifest that when the ratio of the hyperon-to-nucleon couplings increases, all hyperons appear towards low baryon density direction.

The Origin of the Flat Rotation Curves in Spiral Galaxies: The Hidden Roles of Glitching SMDEOs and Emission of Gravitational Waves

Supermassive DEOs (SMDEOs) are cosmologically evolved objects made of irreducible incompressible supranuclear dense superfluids: The state we consider to govern the matter inside the cores of massive neutron stars. These cores are practically trapped in false vacua, rendering their detection by outside observers impossible. Based on massive parallel computations and theoretical investigations, we show that SMDEOs at the centres of spiral galaxies that are surrounded by massive rotating torii of normal matter may serve as powerful sources for gravitational waves carrying away roughly 1042 erg/s. Due to the extensive cooling by GWs, the SMDEO-Torus systems undergo glitching, through which both rotational and gravitational energies are abruptly ejected into the ambient media, during which the topologies of the embedding spacetimes change from curved into flatter ones, thereby triggering a burst gravitational energy of order 1059 erg. Also, the effects of glitches found to alter the force balance of objects in the Lagrangian-L1 region between the central SMDEO-Torus system and the bulge, enforcing the enclosed objects to develop violent motions, that may explain the origin of the rotational curve irregularities observed in the innermost part of spiral galaxies. Our study shows that the generated GWs at the centres of galaxies, which traverse billions of objects during their outward propagations throughout the entire galaxy, lose energy due to repeatedly squeezing and stretching the objects. Here, we find that these interactions may serve as damping processes that give rise to the formation of collective forces f∝m(r)/r, that point outward, endowing the objects with the observed flat rotation curves. Our approach predicts a correlation between the baryonic mass and the rotation velocities in galaxies, which is in line with the Tully-Fisher relation. The here-presented self-consistent approach explains nicely the observed rotation curves without invoking dark matter or modifying Newtonian gravitation in the low-field approximation.

Nucleon Finite Volume Effect and Nuclear Matter Properties in a Relativistic Mean-Field Theory

Effects of excluded volume of nucleons on nuclear matter are studied, and the nuclear properties that follow from different relativistic mean-field model parametrizations are compared. We show that, for all tested parametrizations, the resulting volume energy al and the symmetry energy J are around the acceptable values of 16 MeV and 30 MeV, and the density symmetry L is around 100 MeV. On the other hand, models that consider only linear terms lead to incompressibility Ko much higher than expected. For most parameter sets there exists a critical point （pc, δc）, where the minimum and the maximum of the equation of state are coincident and the incompressibility equals zero. This critical point depends on the excluded volume parameter r. If this parameter is larger than 0.5 fm, there is no critical point and the pure neutron matter is predicted to be bound. The maximum value for neutron star mass is 1.85M⊙, which is in agreement with the mass of the heaviest observed neutron star 4U0900-40 and corresponds to r = 0.72 fm. We also show that the light neutron star mass （1.2M⊙） is obtained for r ≌ 0.9 fro.

Constraints on the skewness coefficient of symmetric nuclear matter within the nonlinear relativistic mean field model

Within the nonlinear relativistic mean field(NLRMF) model, we show that both the pressure of symmetric nuclear matter at supra-saturation densities and the maximum mass of neutron stars are sensitive to the skewness coefficient, J_0, of symmetric nuclear matter. Using experimental constraints on the pressure of symmetric nuclear matter at supra-saturation densities from flow data in heavy-ion collisions and the astrophysical observation of a large mass neutron star PSR J0348+0432, with the former favoring a smaller J_0 while the latter favors a larger J_0, we extract a constraint of -494 MeV≤J_0≤-10 MeV based on the NL-RMF model. This constraint is compared with the results obtained in other analyses.

R-mode instability of strange stars and observations of neutron stars in LMXBs

Using a realistic equation of state （EOS） of strange quark matter, namely, the modified bag model, and considering the constraints on the parameters of EOS by the observational mass limit of neutron stars, we investigate the r-mode instability window of strange stars, and find the same result as in the brief study of Haskell, Degenaar and Ho in 2012 that these instability windows are not consistent with the spin frequency and temperature observations of neutron stars in low mass X-ray binaries.

Effects of Δ-Isobars on Neutron Stars

We have investigated the possibility of the presence of the deltas in neutron star matter and their effects on neutron stars. Δ-meson couplings of the theoretical predictions are only restricted in a region where the deltas can be present and even a first-order phase transition may take place, making the EOS sorer and the maximum mass of neutron stars smaller. The presence of the deltas leads to the rapid decrease of neutrino mean free paths.